Stents are bioprosthetic devices that are typically used for counteracting restenosis, or the repeated narrowing of a blood vessel. Stents may also be used, for example, as shown in U.S. Patent Application 2006/0149360 to Schwammenthal, et al, as a component of a stent-mounted heart valve with mounted leaflets. The stent mounted valve implant described there includes clamping fingers that secure its position at a native valve orifice of the heart.
Such an implant is delivered to its site in the heart using a catheter assembly. To pass through the catheter, the prosthetic valve must be collapsed to a smaller profile. However, since the stent-mounted prosthetic valve has leaflets of pericardium material, it cannot be delivered to the hospital or medical facility in a collapsed or compressed state. Rather, the step of collapsing the implant for passage through the delivery device must be carried out shortly before the implantation procedure. Consequently, the valve, in an open state, is delivered to the user in a container and that container typically contains a sterile, preservative medium such as glutaraldehyde.
Thus, prior to the implantation procedure, the stent-mounted valve must first be manually removed from the storage medium package, collapsed (perhaps by crimping), and then loaded into the delivery catheter in that crimped state.
Several cautions are to be observed prior to and during the step of loading the stent-mounted prosthetic valve. Since the material making up the stent is easily deformed or damaged, the stent must be handled with great care. Secondly, the stent must be crimped or otherwise collapsed to the smaller profile so that it fits properly inside of the catheter delivery tube. The step of collapsing the stent is a delicate process and, if not performed properly, may cause delay the implantation procedure or may entail excessive handling of the stent or even damage to the valve. Removal of the stent from the glutaraldehyde liquid medium in the storage and delivery container by surgically-gloved surgical personnel may be awkward.
Specialized tools may be used to minimize the risks associated with preparing the stent-mounted valve for the step of implanting the prosthetic valve in the heart.
U.S. Patent Application No. 2004/0186563, to Lobbi, discloses a heart valve that is loaded into the delivery catheter using a specialized tool. The valve is crimped or collapsed to a smaller profile by pulling it through a conical-shaped region of the specialized tool. One or more filaments threaded through the valve to allow such pulling and consequent crimping of the valve. A drawback to this procedure is that the step of threading the filaments through the valve can be a tedious and time-consuming process. Also, since the filaments have no purpose after the crimping step, they must be removed from the implant prior to the delivery procedure. Removal of the filaments may cause damage to the valve and may even partially undo the crimping step.
U.S. Patent Application No. 2003/0225445 to Derus et al., describes a loading device having a conical-shaped region for facilitating the collapse of a stent. As with the Lobbi procedure, a filament or the like is used to pull the stent through the loading device to collapse it.
Other devices for transferring a stent from a storage container to a delivery tool are described in U.S. Pat. No. 6,090,035 to Campbell, U.S. Pat. No. 5,693,066 to Rupp et al., U.S. Pat. No. 6,123,720 to Anderson et al., and European Patents WO 98/22044 and WO 97/09946, both to Borghi.
None of these patents or patent applications show the device and procedures described further hereinbelow, nor do they satisfactorily solve the problems which have been described above relating to transfer of the valve from a storage device, in which the valve is in an expanded state, to the delivery tool, in which the valve is in a substantially compressed state.
There is thus a need for a tool that allows for transfer of the valve or other prosthetic device from the storage container to the catheter delivery tube, in a relatively simple manner that requires only minimal handling.